OLED, as a new type of display technology, has unique advantages such as self-illumination, wide viewing angle, low power consumption, high efficiency, thin, rich colors, fast response, extensive application temperature range, low driving voltage, applicable for flexible and transparent display panel, and environmental friendliness, etc. Therefore, OLED technology can be applied to flat panel displays and new generation of lighting, or can be used as backlight of LCD.
OLED is a device made through spin-coating or depositing organic material layers between two electrodes. A classic three-layer OLED comprises a hole transport layer, a light emitting layer and an electron transport layer. The holes injected from the anode and hopping through the hole transport layer, and the electrons injected from the cathode and hopping through the electron transport layer combine to form excitons in the light emitting layer and emit light. By changing the materials of the light emitting layer, the OLED can emit red, green and blue light. Therefore, stable, efficient organic light-emitting materials with pure colors play an important role in the application and promotion of OLEDs, and are urgently needed for the application and promotion of large area panel display in OLEDs.
Among three primary colors (red, blue, green), the red and green emitting materials have made great development, which also meet the market demands of the panels. There are a series of commercially available materials for the blue light emission, such as 4,4′-bis(2,2′-diphenyl vinyl)-1,1′-biphenyl (DPVBi) compounds produced by Idemitsu are widely used in the early period. The devices made by this type of compounds have high efficiency, but these materials often have poor stability, and even worse, this type of compounds often emit sky-blue light, with CIEy>0.15. Therefore, its poor stability and impure color greatly restrict the application of this type of compounds in the full-color display devices. Some other blue-light materials, such as ADN and tetra-butyl perylene made by Kodak, have relatively poor luminous efficiency and cannot be widely used.
